The Brat carbs were not the best. The NV's were made of brittle metal. You might want to disassemble yours and check the internal casting. My Brat .25 had a whole bunch of flash covering up the lower openings of the bypasses (correct term?). After filing all of the flash off and installing a Magnum carb it's a great running engine. It is also very light because mine is AAC.

David